Large stadium structures are currently being designed with rigid dome or roof structures comprised of movable elements that are retractable to provide for open air events in clement weather but can be closed and made weather-tight when desired. Because of design and/or construction constraints, it is typical to provide gaps of significant dimension between adjacent, rigid roof sections, when the sections are in their "closed" configuration. In order to make the structure weather-tight, it has been proposed to utilize inflatable pneumatic seals, which are expandable under internal pneumatic pressure to close and seal the gap between adjacent roof sections.
In a representative stadium roof design, gaps between adjacent rigid roof sections may be as much as 16 inches or greater, and may extend over a length of, for example, 600 or 700 feet. A pneumatic seal for bridging and closing such a gap must of necessity have a very large cross section when fully pressurized. This is turn gives rise to significant problems when the seal is depressurized, because the unit (at least one of conventional design) loses structural stability and can be unpredictably distorted by wind, for example, or portions of the seal may be improperly positioned so as to interfere with proper inflating and sealing and/or be subject to possible damage.
In accordance with the present invention, a novel and improved large scale inflatable pneumatic seal is provided which is formed with primary and secondary internal chamber structuring, forming in essence primary and secondary chamber areas which are separately inflatable. When the primary chamber of the seal is inflated, the seal is caused to assume a desired shape for bridging the gap and forming a weather-tight seal between adjacent rigid roof sections. When the primary chamber is depressurized, to deactivate the seal between roof sections, the seal is caused to assume a second, positively controlled configuration, by increasing the level of pressurization of the secondary chamber. In this manner, a pneumatic seal of very large cross section, and substantial length is maintained under effective physical control at all times.
In the construction of a typical sealing element according to the invention, the secondary chamber is comprised of a plurality of subchambers, so that during pressurization of the secondary chamber, the cross sectional configuration of the seal is relatively thin in the sealing direction and relatively wide in the nonsealing direction. When the primary chamber is inflated, the seal assumes a somewhat oval cross sectional configuration, enabling it to bridge and seal a wide and variable gap between adjacent roof sections.
In a particularly advantageous form of the invention, the secondary chamber may be maintained continuously under a relatively low positive pneumatic pressure. The primary chamber, which is periodically pressurized to effect closing and sealing and depressurized for opening and retracting, is inflated to a somewhat higher pressure than the secondary chamber. Accordingly, when the primary chamber is pressurized for sealing, the secondary chamber is partially collapsed under the effect of the greater pressure surrounding it, within the primary chamber.
Most advantageously, for sealing elements of very great length, such as will be typical for stadium roof seals, the seals can be manufactured in modular sections. Each such section, according to the invention, is provided with a self-contained, sealed secondary chamber. The individual modules are then sealed end to end during installation so as to provide, in the installed unit, a primary chamber of continuous length enclosing a plurality of separate secondary chambers.
For a more complete understanding of the above and other features and advantages of the invention, reference should be made to the following detailed description of a preferred embodiment and to the accompanying drawings.